Field of the Invention
The present invention relates to a shutter apparatus of an electronic front curtain system.
Description of the Related Art
Japanese Patent Laid-Open No. (“JP”) 7-56211 discloses a shutter apparatus that includes two pairs of light shields and two pairs of stepping motors connected to the light shields and configured to open and close an aperture in a lens through the light shields. This configuration can drive each of front and rear curtains in the shutter by driving each stepping motor.
One conventionally proposed imaging apparatus includes a focal plane shutter for a camera and an electronic shutter and uses them for an imaging action. This imaging apparatus captures an image through rear blades including a mechanical shutter and the electronic shutter configured to provide reset scanning of pixels on the image sensor before the rear curtain runs. The blades include a plurality of arms, a shutter blade, and a pivot member, and reciprocate between a position at which the blades cover the aperture in a shutter base plate and a retreat position. The charge accumulation start scanning (reset scanning) on the image sensor has a scanning pattern suitable for a scanning characteristic of the mechanical shutter in the rear curtain.
The thus configured shutter needs to shield light through the rear blades so as to prevent the image sensor from being exposed in reading the electric charges after the image is captured from the image sensor. For the next imaging, an exposure action is performed after the shutter base plate in the mechanical shutter is moved from the light shielding state to the opening state. The shutter having the front blades can restore to a pre-capturing standby state without exposing the image sensor, by charging the front blades and the rear blades in this order in reading the electric charges from the image sensor after the image is captured. Hence, in comparison with the shutter apparatus that includes the front blades and the rear blades, a release time lag in consecutive shooting and a low frame rate are problematic. For a higher frame rate, the front blades may be provided so as to shield light from the image sensor, the front and rear blades may be charged in reading the electric charges, and the state may be restored to the pre-captured standby state.
However, when the focal plane shutter and the electronic shutter are used for the imaging action by providing the light-shielding front blades, the shutter apparatus in JP 7-56211 needs an actuator for controlling the front blades. Hence, the shutter apparatus becomes large and the manufacturing cost increases.